71–76 of 76 posts
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Why bother with the rocket? It sounds mad, but you can actually just send the balloon. to orbit... http://www.jpaerospace.com/atohandout.pdf
Why do they need the space station part?
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I can't get my head around how this thing works. Apart from the direct GPS signal it's able to also receive the part of it that was reflected by the ocean? How does the reflected signal tell anything about the wind speed? And btw what are star trackers used for? As a fallback for GPS?
The earth is bathed in radiation from GPS transmitters and these clever satellites are using doppler radar techniques to see how those signals are being reflected from ocean waves. From the doppler shift you can infer wind fields. Consumer GPS receivers only compute position from these signals, but there is a lot of interesting science you can do from the raw signals with a hacked GPS receiver.
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Launching from the equator is useful for a wide range of orbits as a component of the final vector 1600km/h is really not that fast and your final orbit crosses the equator anyway. The only issue is if the ideal launch point is not over the ocean. Also, there is a wide band near the equator with close to optimal velocity.
It's about 5% of the final velocity, but that's way more than 5% fuel savings because you don't have to suspend million of pounds against gravity for a minute and also don't have to accelerate that fuel. For example Saturn V used 40% of its total fuel to get up to this speed. That's a huge savings. Unless I am reading the data incorrectly: http://www.braeunig.us/apollo/SaturnV.pdf
Orbital ATK has been building and launching the Pegasus XL ( https://www.orbitalatk.com/flight-systems/space-launch-vehic... ) for a bit now. It is an extremely cheap platform that is launched from an airplane. What's neat is the User Manual is available online: https://www.orbitalatk.com/flight-systems/space-launch-vehic... [pdf]
Extremely cheap? Initially it was $6mm, now it costs almost as much as a Falcon 9 launch. Part of that is due to its extremely low launch rate -- this was the first launch since 2013 -- but still.
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Extremely cheap? Initially it was $6mm, now it costs almost as much as a Falcon 9 launch. Part of that is due to its extremely low launch rate -- this was the first launch since 2013 -- but still.
if Orbital launched as much as SpaceX, the Pegasus cost before margin could be 20% of what it is today.
Lifting a rocket that high before firing it carries another benefit besides the (small) altitude gain and lower fuel requirements due to drag: Max Q, the maximum dynamic pressure that has to be sustained by the rocket usually happens at a lower altitude than that (depending on the mission). This means your rocket has to sustain a far lower structural load, making it safer and lighter.
Max Q for the Peagus and Saturn V are actually at the exact same altitude. ~14-16km. And nearly identical pressures. The thing is because all rockets follow the same trajectory to orbit, The gravity curve. So you hit similar speeds at similar altitudes. If you don't, you either aren't making it to orbit, or you're wasting fuel. This is because the gravity curve is a straight line if you ask Einstein, just earth's gra…